1. Field of the Invention
The present invention relates to an illuminating device, and more particularly, to an illuminating device having a structure different from that of conventional illuminating devices.
2. Description of Related Art
In recent years, people have made effort to develop new types of lighting sources. Light emitting diode (LED) has advantages of power saving, durable, and small size, which are hardly comparable with traditional lighting sources (such as incandescent lamp and fluorescent lamp). Hence, light emitting diode is generally acknowledged as the most valuable “green” lighting source in the new century, and could become a leading product in the lighting market by replacing incandescent lamp and fluorescent lamp.
Specifically, light emitting diode belongs to semiconductor devices, and is mainly made of compounds of group III-V elements, such as gallium phosphide (GaP) or gallium arsenide (GaAs). Light emitting diode is to release superfluous energy in a light with a specific wavelength range by applying a current to a compound semiconductor and combining electrons with electron holes. Since luminescence of light emitting diode is not through heating or discharging, light emitting diode has a life span of 100000 hours or more, and better photoelectric conversion efficiency than traditional lighting sources.
FIG. 1 is a partial three-dimensional schematic view of a conventional illuminating device which uses a light emitting diode as its light source, and FIG. 2 is a cross-sectional schematic view along a section line A-A in FIG. 1. Referring to both FIG. 1 and FIG. 2, in a conventional illuminating device 100 which uses a light emitting diode as its light source, the position of a circuit board 120 disposed in a hollow body 110 of the illuminating device 100 is limited by a pair of hooking portions 112 disposed on a side wall of the hollow body 110, wherein the hooking portions 112 are located on an opening end 110a of the hollow body 110 relatively near a heat sink (not illustrated). From FIG. 1 and FIG. 2, it can be seen that the hollow body 110 and the circuit board 120 have necked-down portions 114 and 122, respectively. Therefore, when the circuit board 120 is inserted into the hollow body 110 from the opening end 110a with a larger bore, the necked-down portion 122 of the circuit board 120 is supported by the necked-down portion 114 of the hollow body 110, and then by the hooking portions 112 leaning against the circuit board 120, the circuit board 120 would be confined in the hollow body 110.
However, under such disposition structure, due to limitation on the position of the hooking portions 112, the size of the circuit board 120 cannot be increased effectively. In addition, as the hooking portions 112 are located on the opening end 110a of the hollow body 110 relatively near a heat sink (not illustrated), and the hooking portions 112 are formed by hollowing out a portion of a side wall of the hollow body 110, when a thermal compound (not illustrated) is filled into the hollow body 110, the thermal compound (not illustrated) can easily leak from a hollowed-out portion 116.